Practical two-party SM2 signing using multiplicative-to-additive functionality

Threshold signatures are important tools for addressing issues related to key management, certificate management, and cryptocurrencies. Among them, two-party SM2 signatures have received considerable interest recently. In this paper, we propose a fast and secure online/offline two-party SM2. By employing the re-sharing technique, we have successfully made the online phase of the signing process non-interactive while achieving nearly optimal computational efficiency. Additionally, in the offline phase, there is just a single call to the multiplicative-to-additive functionality based on Paillier encryption. Our protocol is existentially unforgeable under adaptive chosen message attacks in the random oracle model in the presence of a static adversary. Experimental results demonstrate that our proposed scheme outperforms previous similar schemes by approximately a factor of 2 in online computation and a factor of 3 in online communication. Our scheme can be applied in scenarios such as Certificate Authority (CA) and the signing of blockchain transactions to provide them with a more secure and flexible implementation method, enhancing the security and reliability of the systems.